The two men met in Cardiff for the first of nine (!) official debates before the party chooses its leader on 24 September.

Supporters of both campaigns have accused the other side of peddling untruths.

Corbyn: ‘I didn’t say that’

Owen Smith said he wants a second EU referendum, and said Corbyn failed to fight hard enough to keep Britain in.

He accused Mr Corbyn of making a “real mistake” by apparently calling for the government to trigger Article 50 of the Treaty on European Union, beginning the legal process of leaving the bloc.

“No, I didn’t say that”, Mr Corbyn interrupted.

It didn’t take long for Smith supporters to unearth a video of Mr Corbyn saying something very close to that in an interview with the BBC on 24 June, the morning of the referendum result.

Mr Corbyn in fact said: “The British people have made their decision. We must respect that result and Article 50 has to be invoked now so that we negotiate an exit from European Union.”

Later in the debate he said his remarks had been wrongly interpreted.

“I said it was inevitable Article 50 was going to be triggered. This was immediately interpreted as being that it should be triggered immediately.

“Maybe I can choose my words more carefully at the point. It is going to be triggered at some point.”

As a section of the crowd began to jeer, Mr Corbyn added: “All right, okay, well… mea culpa.”

Corbyn: ‘We were ahead in May’

Mr Corbyn was forced to defend Labour’s record in the various elections that have been held during his leadership after Mr Smith said he was making it harder for the party to win.

The Labour leader suggested that it was the unrest caused by Labour MPs’ efforts to oust him that had led to a slump in support in the polls.

Mr Corbyn said: “We won all four by-elections, three with a big swing to Labour. We won four mayoral contests.

“We’ve picked up a lot of support over the general election of 2015 and so I think as an opposition we’ve done very well.

“We were ahead in May. Then came the wave of resignations. Then came the threat to unity in the party. And that is what has put us behind in the polls.” [*See update below]

But no major polling company put Labour ahead in May.

Since Mr Corbyn became leader last September, only three voter intention polls out of 86 have put Labour ahead of the Tories, one in March and two in April.

It’s true that the Tories’ lead has grown since May, but it’s impossible to say whether this is the result of disunity in the Labour party as opposed to the Brexit result or Theresa May becoming Prime Minister.

Mr Corbyn’s broader point that Labour have “done very well” as an opposition party is highly debatable.

It’s true that Labour has experienced a surge in membership since Corbyn became leader. Labour now has more than half a million members, dwarfing every other UK party, according to the House of Commons Library.

There’s no post-war precedent for such a sharp rise, so it’s hard to say whether this will affect the party’s electoral fortunes.

It’s also true that Labour have won mayoral contests and by-elections, though few psephologists would draw any conclusions from this small number of victories about the party’s chances at the next general election.

Experts do take an interest in the results of local elections though.

Labour did better than the polls predicted in the 2016 English council elections, losing a tiny number of council seats rather than the hundreds expected.

But it was hard to spin this as a success, since opposition parties almost always gain seats in local elections.

Professor Tony Travers from the LSE notes that since 1979, only opposition parties that gain a massive lead over the incumbent party in local elections go on to form the next government.

Models that use local election results to predict the outcome of the next general election, like this one from Chris Prosser of the British Election Study – also suggest an emphatic Conservative victory.

Smith ‘victory’ poll was a hoax

Some Smith supporters got very excited about a snap poll circulating on Twitter that appeared to show their man as the winner of the first debate.

The research was attributed to YouGov, but the polling company quickly squashed it as a fabrication.

No reputable pollster has published a snap poll, so it’s hard to call the first debate for either candidate.

For what it’s worth, bookmaker William Hill said that they had shortened the odds slightly on a Corbyn victory after the debate, suggesting punters preferred him to Owen Smith.

[Update: a spokesman for Jeremy Corbyn says the words “we were ahead in May” referred to the results of the English council elections rather than opinion polling.

The spokesman said: “According to the BBC, Labour won 31 per cent of the national share of the vote at the May local elections compared with 30 per cent for the Tories.

“Therefore, when it really counted – at an actual election – we were ahead in May, as Jeremy was correct to state.”]

Your headline is misleading. It implies that both candidates were found to have lied during the debate and then you offer no evidence that Owen Smith did. In addition, are you sure the false YouGov poll actually emanated from the Smith camp? That’s what you need to substantiate to demonstrate their culpability- getting excited about apparently good news isn’t the same as lying.

“Lies on both sides”? You had to pluck a twitter meme from who knows where to off-set untruths from the mouth of one of the candidates?
What your article is saying is that Corbyn was not entirely honest in his answers during the Hustings.
Smith, in contrast, was.
Thanks for confirming this.

Jeremy Corbyn’s comment ‘we were ahead in May’ is clearly and provably correct, therefore not a lie. The projected national share of the vote from the May council elections is much more accurate than any poll and it put Labour on 31% to the Tories’ 30% (source: BBC). Therefore Labour was incontrovertibly ahead in May, regardless of what polling organisations said at the time. Jeremy Corbyn’s statement is therefore true, so you have no grounds to call it a ‘fiction’.

Corbyn has been totally against Europe for donkeys years then on attaining the leadership he suddenly changes his tune. Acting like the Pied Piper he flushes away everyone else’s principles down the pan with him. Dennis Skinner seen sense and at the last minute reverted to voting out. Last April George Galloway pleaded for Corbyn
to change tack and vote for what he believed in otherwise it would be fatal for Labour.
And there we go…

The comments here are very frightening to me. They show the absolute inability of Corbyn supporters to see anything he says as untrue or even misleading. They are firmly convinced that he and presumably the shadow chancellor are always right even when they have been demonstrably wrong.
That’s terrifying.

Oh, come on! It isn’t biased just because you don’t like its findings. Factcheck is an excellent, neutral resource based on reputable sources and evidence. Crying ‘anti-Corbyn bias’ at the slightest (and justified) criticism does not help your cause at all.

OK!!! You’ve made points about JC peddling untruths. So when will we see the points about OS peddling untruths, since you’ve seemed to miss that bit out in this article which has the title – “FactCheck: Lies on both sides in Labour leadership battle”???

Labour under Corbyn may well have been a point ahead in May but this was for the English Council Elections where the vast majority of seats are not up for grabs. These were held mainly Labour areas of England and Labour should have done well but didn’t. Where Labour needs to win in Scotland (vote down again and also in MSPs) and Wales (vote down again and one seat lost) doesn’t seem to figure in the ‘Corbyn facts’. Indeed in 2014 Labour were a point ahead in those Local Elections and went onto lose again in 2015. At the 2012 elections Labour were on 39% and the Tories on 33% according to Rawlings and Thrasher.

Whether you take the PNS and NEV on such a small vote, Corbyn has the same problem as Milliband. To win a General Election Labour needs to do well in England and win in Wales and Scotland. In the run up to the 1997 GE Labour under Blair had leads of up to 22% over the Tories at local elections. Corbyn has 1%. Hardly worth shouting about but Corbyn does.

Jeremy Corbyn reminds us of Michael Foot. Both are courteous gentlemen with policy ideas springing out in all directions. But, neither of those ‘puddings’ has a theme.
It’s where we were in at the election of 1983. Michael and his supposed left-wing supporters came up with what became known as the ‘longest suicide note in history’. Lots of promises to enlarge the public sector but little of relevance to ordinary voters.
We lost in 1983 by the widest margin in that century. Leader Foot did the decent thing and retired. He was replaced by the loquacious Neil Kinnock who’s claim to fame (or infamy) is that he faced down the militants at Conference.
Labour is the only UK Party that can prove brings greater equality. Not just in terms of household incomes but across the wide spectrum of discriminations and exclusions. Whereas the Tories and L-Ds promote inequalities and injustices in the name of the wealthy classes.
That’s the clear aim we need. Not Corbynomics or more State control of our lives.

>“We were ahead in May. Then came the wave of resignations. Then came the threat to unity in the party. And that is what has put us behind in the polls.”
But no major polling company put Labour ahead in May.

You have heard of red herrings? You are well aware the words “We were ahead in May” referred to the English council elections.

>”We must respect that result and Article 50 has to be invoked now so that we negotiate an exit from European Union.”

The word has a variety of senses. It need not mean “immediately”.

O.E.D. definition 1.b under the present circumstances; in view of what has happened.